Electrode construction



Aug. 9, 1932. FRlTz 1,871,363

ELECTRODE CONSTRUCTION Filed Sept. 20, 1950 BMW/ax 53m KL. gm

MGXW

Patented Aug. 9, 1932 UNITED STATES PATENT; OFFlCiE EABL .A. FRITZ, OF MILWAUKEE, WISCONSIN, ASSIGNOR TO CUTLEB- u u INCL, OF MILWAUKEE, WISGONSIN, A COBFOBATION OF DELAWARE ELEOTZBODE CONSTBUGI'IOH Application filed September 20, 1980. 'Berial No. 483,180.

This invention relates to electron discharge tubes having a'controlling electrode or grid, and has for its object to improve the operation and increase the life of such tubes.

It has been found that in electron tubes having cathodes coated with alkaline earth oxides these oxides are gradually vaporized and partially deposited on the control grid. During operation the grid due to the deposited oxides gives rise to secondary emission, which greatly impairs the efficiency of control by the grid.

It has been known that grids made of certain metals have a low initial secondary emission and that such emissions can be still further reduced by oxidation of the grid surface. But the deposition on the grid of alkaline earth oxides from the cathode gradually increases the secondary emission to the point where the operation of the tube becomes unsatisfactory.

l have found that by making the grid of tantalum and oxidizing its surface the initial secondary emission is smaller than that observed with most other materials, while at the same time it is not appreciably increased by the deposition of oxides from the cathode.

Referring to the drawing, 1 is a glass bulb of a conventional electron tube; 2 is a filamentary cathode which is coated with alkaline earth oxides to increase its emission; 3 is a grid having a surface layer of tantalum oxide, and 4; is an anode. The cathode which preferably comprises barium or strontium may be prepared in any Wall known manner. The anode may be made of any suitable material. The grid which may beof any suitable shape and constructed of tantalum may be treated in any preferred manner to obtain the surface layer of tantalum oxide.

While no definite explanation can be given of the phenomenon, it is believed that the tantalum oxide counteracts the emission increasing eifect of the alkaline earth oxides de posited on the grid, and thus prevents an increase of the secondary emission from the latter.

What I claim as new and desire to secure by Letters Patent is:

1. An electron discharge device, having a cathode coated with an emission increasing substance and a grid having a surface of tantalum oxide.

2. An electron tube, having a cathode of alkaline earth oxides and a grid of tantalum oxide.

3. An electron tube, having a cathode of barium and strontium oxide and an oxidized tantalum grid.

4. An electron discharge device having main electrodes and a control grid whose surface is of tantalum oxide.

In witness whereof, I have hereunto subscribed my name.

EARL A. FRITZ. 

